Response of convection electric fields in the magnetosphere to IMF orientation change

Nishimura, Y.; Kikuchi, Takashi; Wygant, J. R.; Shinbori, Atsuki; Ono, Takayuki; Matsuoka, A.; Nagatsuma, Tsutomu; Brautigam, D. H.

doi:10.1029/2009ja014277

Cited by 23 publications

(24 citation statements)

References 32 publications

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“…[33] Early observations of near-Earth convection by Aggson and Heppner [1977] showed the presence of large electric field in the inner magnetosphere during the substorm growth phase. Recently Nishimura et al [2009] also found that convective electric field enhancement in the inner magnetosphere has a very small time delay (∼5 min) relative to IMF southward turning, whereas electric field enhance-ment in the outer magnetosphere has a more pronounced delay (∼30 min). Our work is consistent with this picture: delayed response in the outer magnetosphere is caused by storage of magnetic flux in the tail and suppression of earthward convection, whereas the onset of the flux transport is likely related to the release of magnetic flux due to tail reconnection.…”

Section: Discussionmentioning

confidence: 93%

Superposed epoch analysis of magnetotail flux transport during substorms observed by THEMIS

et al. 2011

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Cumulative magnetic flux transport earthward/tailward of the reconnection site in the plasma sheet or equatorward toward the neutral sheet (Φ) has been shown to be one of the most useful quantities for remotely sensing reconnection onset in the magnetotail. We examine the behavior of Φ during substorms near the onset meridian using superposed epoch analysis of Time History of Events and Macroscale Interactions during Substorms (THEMIS) probe observations at different downtail distances. Observational data come from the THEMIS Substorm Database, assembled under the auspices of the Geospace Environment Modeling (GEM) program (http://www.igpp.ucla.edu/themis/events/). We find that Φ starts to increase a few minutes prior to ground midlatitude Pi2 onset. Although our study cannot monitor regions beyond 30 RE, the apogee of the most distant probe (P1), enhanced transport tends to begin at 20–30 RE and moves progressively inward just prior to ground Pi2 onset. Our results are consistent with recent THEMIS case studies showing that reconnection initiates the substorm expansion phase process.

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Section: Discussionmentioning

confidence: 93%

Superposed epoch analysis of magnetotail flux transport during substorms observed by THEMIS

et al. 2011

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“…However, for strong magnetic field at low altitudes, diffusion is very slow and results in very weak fluxes of energetic electrons for forbidden drift shells. In contrast, geomagnetic storms, large substorms, and sudden commencements or magnetospheric compressions are accompanied by a very strong penetrating EF in the dawn-dusk direction of approximately a few mV/m [e.g., Nishimura et al, 2006Nishimura et al, , 2009Shinbori et al, 2006;Fejer et al, 2007;Lazutin and Kuznetsov, 2008]. On the nightside, this EF is pointed westward and results in the fast (a few hours) ExB drift of particles across magnetic field lines toward the Earth.…”

Section: Discussionmentioning

confidence: 99%

TEC evidence for near‐equatorial energy deposition by 30 keV electrons in the topside ionosphere

et al. 2013

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[1] Observations of energetic electrons (10 -300 keV) by NOAA/POES and DMSP satellites at heights <1000 km during the period from 1999 to 2010 allowed finding abnormal intense fluxes of~10 6 -10 7 cm À2 s À1 sr À1 for quasi-trapped electrons appearing within the forbidden zone of low latitudes over the African, Indo-China, and Pacific regions. Extreme fluxes appeared often in the early morning and persisted for several hours during the maximum and recovery phase of geomagnetic storms. We analyzed nine storm time events when extreme electron fluxes first appeared in the Eastern Hemisphere, then drifted further eastward toward the South-Atlantic Anomaly. Using the electron spectra, we estimated the possible ionization effect produced by quasi-trapped electrons in the topside ionosphere. The estimated ionization was found to be large enough to satisfy observed storm time increases in the ionospheric total electron content (TEC) determined for the same spatial and temporal ranges from global ionospheric maps. Additionally, extreme fluxes of quasi-trapped electrons were accompanied by the significant elevation of the low-latitude F-layer obtained from COSMIC/FORMOSAT-3 radio occultation measurements. We suggest that the storm time ExB drift of energetic electrons from the inner radiation belt is an important driver of positive ionospheric storms within low-latitude and equatorial regions.

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“…The EIW model predicts that the electric field associated with the ionospheric currents is transmitted into the magnetosphere by the Alfven waves along the magnetic field lines. Thus, the PI electric field is detected by the HF Doppler observations in the low‐latitude F region ionosphere [ Kikuchi , ] and by satellites in the inner magnetosphere [ Nishimura et al ., ]. Furthermore, upward flow of the Poynting flux was observed in the inner magnetosphere as predicted by the EIW model [ Nishimura et al ., ].…”

Section: Introductionmentioning

confidence: 97%

Transmission line model for the near‐instantaneous transmission of the ionospheric electric field and currents to the equator

Kikuchi

2014

JGR Space Physics

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The simultaneous onset of the preliminary impulse (PI) of the geomagnetic sudden commencement at high latitude and dayside dip equator is explained by means of the TM 0 mode waves propagating at the speed of light in the Earth-ionosphere waveguide (EIW) [Kikuchi et al., 1978]. A couple of issues remain to be addressed in the EIW model: (1) How is the TM 0 mode wave excited by the field-aligned currents (FACs) in the polar region? (2) How are the quasi-steady ionospheric currents achieved by the TM 0 mode waves? (3) How simultaneous or delayed are the onset and peak of the equatorial PI with respect to the high-latitude PI? To address these issues, we examine the TEM (TM 0 ) mode wave propagation in the finite-length transmission lines replacing the pair of FACs (magnetosphere-ionosphere (MI) transmission line) and the Earth-ionosphere waveguide (ionosphere-ground (IG) transmission line). The issue (1) is addressed by showing that a fraction of the TEM mode wave is transmitted from the MI to IG transmission lines through the polar ionosphere. To address the issues (2) and (3), we examine the properties of the finite-length IG transmission line with finite ionospheric conductivity. It is shown that the ionospheric currents start to grow instantaneously and continue to grow gradually with time constants of 1-10 s depending on the ionospheric conductivity. The MIG transmission line enables us to explain the instantaneous onset and delayed peak time of the equatorial PI and quick electric field response of the low-latitude ionosphere and inner magnetosphere.

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Response of convection electric fields in the magnetosphere to IMF orientation change

Cited by 23 publications

References 32 publications

Superposed epoch analysis of magnetotail flux transport during substorms observed by THEMIS

Superposed epoch analysis of magnetotail flux transport during substorms observed by THEMIS

TEC evidence for near‐equatorial energy deposition by 30 keV electrons in the topside ionosphere

Transmission line model for the near‐instantaneous transmission of the ionospheric electric field and currents to the equator

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